In-the-ear and in-the-canal type hearing aids have become accepted by users for their small size, ease of use and relative comfort, as compared to older style hearing aids. Many of the in-the-ear and in-the-canal type devices include a housing or shell which is designed to fit in the ear or ear canal of the user.
The shell may hold the electronic circuitry, a microphone, and a receiver. The microphone receives audible sound from outside of the device and responsively creates an electronic signal. The signal may be sent to processing circuitry which supplies an output signal to the receiver. The receiver in turn, provides audio output to the ear.
Typically, in the in-the-ear and in-the-canal type devices, sound travels from an output port of the receiver, through a sound channel, and out of the device through an acoustical output port in the hearing aid shell. The sound then travels through the user's ear canal and causes the tympanic membrane to vibrate.
Ears secrete a substance known as cerumen or ear wax. While ear wax cleans the internal structure of the ear, it also tends to flow into the sound channel and receiver of a hearing aid located in the ear. Ear wax which migrates into a hearing aid can degrade the effectiveness of the device and can eventually cause the device to fail.
A number of barrier products are presently available to prevent or reduce the migration of ear wax into a hearing aid. One such barrier design uses a fine mesh screen in the sound channel between the receiver and acoustical output port of the shell.
More recently, barrier systems have been introduced which include a housing which threadedly interconnects the output port of the receiver and the acoustic port of the shell. The housing threads into a portion of the shell. The housing has an interior surface which includes projections extending inwardly thereof, creating a tortuous path for solid or semi-liquid ear wax migrating therethrough.
Such devices are disclosed in Weiss, U.S. Pat. No. 4,870,689, entitled "Ear Wax Barrier For A Hearing Aid" and Weiss et al., U.S. Pat. No. 4,972,488, entitled "Ear Wax Barrier And Acoustic Attenuator For A Hearing Aid," both of which patents are commonly assigned herewith, and both of which patents are incorporated by reference herein.
In the devices disclosed in the Weiss and Weiss et al. patents, the barrier is incorporated into a housing, which has projections extending inward of the housing. The barrier is then threaded into the hearing aid shell. This design was a significant improvement over devices prior thereto.
In addition, attenuation/damping of the sound transmitted by hearing aids assists the user in understanding and perceiving nearby sounds and conversation. Prior wax barriers have also exhibited attenuation and damping characteristics.
There continues to be a need for damping/attenuating structures which are easily inserted into and removed from housings or shells for hearing aids without additional mechanical components and/or shell alterations. Preferably, such structures would also facilitate field installation of one of a plurality of screens having predetermined attenuating/damping characteristics in the hearing aid.